jQuery.fn.center = function(loaded) { 
	var obj = $(this);
	if(!loaded) {
		obj.css('position', 'fixed');
		obj.css('top', $(window).height() / 2 - this.height() / 2);
		obj.css('left', $(window).width() / 2 - this.width() / 2);
		$(window).resize(function() { 
			obj.center(!loaded); 
		});
	} else {
		obj.stop();
		obj.animate({ top: $(window).height() / 2 - this.height() / 2, left: $(window).width()/2-this.width()/2}, 200, 'linear');
	}
} 